The present invention relates to an improved means, in a direct exchange heating/cooling system, of protecting at least one of sub-surface refrigerant transport tubing containment pipes and sub-surface refrigerant transport tubing from corrosive sub-surface elements by means of providing spacer devices, such as spacer fins or the like, so as to keep the pipes/tubing away from direct contact with the ground as the space between the pipes/tubing is filled with a corrosive resistant and heat conductive grout.
Ground source/water source heat exchange systems typically utilize fluid-filled closed loops of tubing buried in the ground, or submerged in a body of water, so as to either absorb heat from, or to reject heat into, the naturally occurring geothermal mass and/or water surrounding the buried or submerged tubing. Water-source heating/cooling systems typically circulate, via a water pump, water, or water with anti-freeze, in plastic underground geothermal tubing so as to transfer heat to or from the ground, with a second heat exchange step utilizing a refrigerant to transfer heat to or from the water, and with a third heat exchange step utilizing an air handler, which is typically comprised of finned copper tubing and an electric fan, to transfer heat to or from the refrigerant to heat or cool interior air space.
Direct exchange (“DX”) heating/cooling systems (also commonly referred to as “direct expansion” ground source/geothermal heating/cooling systems) where the refrigerant transport lines are placed directly in the sub-surface ground and/or water, typically circulate a refrigerant fluid, such as R-22, in sub-surface refrigerant lines, typically comprised of copper tubing, to transfer heat to or from the ground, and only require a second heat exchange step to transfer heat to or from the interior air space by means of an air handler. Consequently, DX systems are generally more efficient than water-source systems because of less heat exchange steps and because no water pump energy expenditure is required. Further, since copper is a better heat conductor than most plastics, and since the refrigerant fluid circulating within the copper tubing of a DX system generally has a greater temperature differential with the surrounding ground than the water circulating within the plastic tubing of a water-source system, generally, less excavation and/or drilling is required, and installation costs are lower, with a DX system than with a water-source system.
While most in-ground/in-water heat exchange designs are feasible, various improvements have been developed intended to enhance overall system operational efficiencies. Several such design improvements, particularly in direct expansion/direct exchange geothermal heat pump systems, are taught in U.S. Pat. No. 5,623,986 to Wiggs; in U.S. Pat. No. 5,816,314 to Wiggs, et al.; in U.S. Pat. No. 5,946,928 to Wiggs; and in U.S. Pat. No. 6,615,601 B1 to Wiggs, the disclosures of which are incorporated herein by reference. Such disclosures encompass both horizontally and vertically oriented sub-surface heat geothermal heat exchange means.
Typically, in DX system applications, the sub-surface refrigerant transport tubing is one of backfilled with natural earth and backfilled with a heat conductive grout material. Generally, the quickest and/or the best geothermal heat transfer results from backfilling the tubing with a heat conductive grout.
A DX system's sub-surface refrigerant transport tubing, which generally always is comprised of copper tubing/lines, is generally impervious to most soils and has an extremely long life expectancy due to the natural properties of copper and the green colored cuprous oxide film that forms on the tubing's surface. However, when copper is installed in sub-surface conditions with a ph below 5.5 or above 11, or in sub-surface conditions that may otherwise be corrosive to copper (such as in sulfur water or near a septic system or the like), a means to protect the copper lines from deterioration is desirable.
Historically, the sub-surface lines of a DX system have been protected via cathodic protection (which is well understood by those skilled in the art), or have simply not been installed in close proximity to corrosive elements. While cathodic protection works well for near surface applications, it is more difficult and expensive to utilize in vertically oriented deep well/borehole tubing applications (a deep well/borehole application is herein defined as being in excess of 100 feet deep).
Further, the simple avoidance of tubing installations in areas of corrosive soils restricts the ability to install DX systems in various applications due to unavailability of sufficient non-corrosive land area for geothermal heat transfer.
While many water-source heat pump system applications utilize tubing spacer devices, such spacer devices are designed to keep the supply and return water transport tubing apart from one another, and are further generally intended to push each respective tube against the natural wall of the well/borehole, as is well understood by those skilled in the art. Since the plastic polyethylene tubing typically utilized in water-source system applications is corrosive resistant, the spacer devices are intended to push the tubes as close as possible to the natural, unexcavated, earth so as to theoretically improve natural heat conductivity, all while keeping the two respective lines as far apart as possible so as to avoid as much as possible of the heat gain/loss “short circuiting” effect inherent in all water-source systems. The “short circuiting” effect is caused by the heat transfer fluid (the entering fluid being cool in the heating mode and warm in the cooling mode) entering the sub-surface heat exchange area through one pipe and exiting the heat exchange area (after the fluid has gained heat in the heating mode and rejected heat in the cooling mode) through an operatively coupled second pipe, which second pipe is typically in close proximity to the first entering pipe of a differing temperature extreme. However, in DX system designs as taught by Wiggs, where the liquid refrigerant transport line is all or mostly insulated and where only the vapor refrigerant transport line is fully exposed, the heat gain/loss “short circuiting” effect is eliminated or minimized, thus there is no need to push the two lines as far apart as possible. Further, since some sub-surface environments can be corrosive to copper, in such instances it is not desirable to push the exposed copper line against the native earth.
Thus, a means to protect the copper refrigerant transport tubing, or other metal refrigerant transport tubing, in a DX system, from corrosive sub-surface environments, absent the necessity of installing an expensive and time-consuming separate cathodic protection system, would be preferred and would extend the application of DX system installations to areas that would otherwise simply be avoided.